What could have significantly affected climatic variations and advances and retreats of ice sheets during the Pleistocene epoch

There are a number of potential causes including Milankovitch cycles which are variations in the orbital eccentricity, axial tilt and precession of the Earth as it orbits the sun. These are thought to have an impact on the climate of the Earth. Also factors such as variations in solar activity and variations in the Earth’s albedo (the amount of solar radiation reflected back into space) are thought to play a part in fluctuations in climate.

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